In a conventional solenoid valve, when current is not applied to a coil, a plunger is urged by a spring. On the other hand, when current is applied to the coil, the plunger is attracted resisting elastic force of the spring, and a fluid passage is opened and closed by a valve element which moves together with the plunger.
In a solenoid valve like this, generation of a noise caused by a collision of the plunger or the valve element and a noise caused by pulsation of fluid is prevented, by reducing a moving speed of the plunger using a damping effect of a damper chamber which is disposed on one end side of the plunger.
Further, in order to improve responsiveness of the solenoid valve when the plunger moves, a solenoid valve is proposed which is provided with a check valve such that the plunger does not act in a direction because the damping effect is unnecessary affected. Note that the check valve provided with a ball, spring and a cap is built in the plunger. Further, the plunger is formed with a fluid passage and a valve seat. (For example, please refer to Japanese Utility Model Application Laid Open No. 5-56717.)
In the conventional solenoid valve, however, since the check valve remains closed and the damping effect is exerted until a pressure difference reaches a valve opening pressure, delay in response of the solenoid valve occurs. Moreover, dispersion in responsiveness of the solenoid valve caused by dispersion in a load of the spring increases. Further, the check valve has a large number of component parts and the plunger requires a lot of additional manufacturing processing such as forming the fluid passage, the valve seat and the like.